text: First we need a set of points that accurately define the contour.
  These points are advected forward using a trajectory
  integration technique.
  To maintain its integrity,
  points must be added to or removed from the curve 
  at regular intervals based on some criterion or metric.
  The most obvious criterion is to maintain the distance between adjacent points
  within a certain interval.
  A better method is to use curvature since fewer points are required for
  the same level of precision.
  The curvature of a two-dimensional, Cartesian curve is given as:
  where  is the radius of curvature 
  and  is the path.
  We need to keep the fraction of arc traced out between two adjacent points,
  <math>
  r \Delta s
   is the path difference between them,
  roughly constant
  In,
  cubic spline fitting is used both to calculate the curvature
  and interpolate new points into the contour.
  The spline, which
  is fitted parametrically,
  returns a set of second-order derivatives.